The finding, from a large clinical trial, promises new hope to people suffering from one of the deadliest kinds of late-stage cancer.

Before the new treatment, only 10% to 20% of patients with what doctors classify as stage IV renal cell carcinoma -- metastatic kidney cancer -- survived for five years. It's a fast-spreading cancer. By the time kidney cancer is discovered, one in three patients already have this advanced stage of the disease.

Alpha-interferon has been the first-line treatment for metastatic kidney cancer. Bernard Escudier, MD, of France's Gustave Roussy Institute, and colleagues gave this standard treatment to 316 patients. An additional 325 patients got interferon plus Avastin, a drug that prevents tumors from growing new blood vessels.

Patients treated with interferon alone saw their disease "progress" -- get worse -- after an average 5.4 months. Those treated with Avastin plus interferon averaged 10.2 months before disease progression.

That was enough for the researchers, who stopped the study at this point. The data strongly suggest that patients receiving the combination treatment would have lived significantly longer than those given interferon alone.

One promising finding was that patients taking the combination therapy were able to cut back on the dose of interferon they were taking without lessening the effect of treatment. This is important, as the flu-like side effects of interferon treatment can greatly affect patients' quality of life.

There's even more hope on the horizon. In an editorial accompanying the study, Robert J. Motzer, MD, of Memorial Sloan-Kettering Cancer Center and Ethan Basch of Cornell University, note that other new cancer drugs -- Sutent and Torisel -- also help patients with late-stage kidney cancer.

The Escudier report and the Motzer/Basch editorial appear in the Dec. 22/29 issue of The Lancet.